Electric resistance



March 5, 1940, E. H. BICKLEY ELECTRIC RESISTANCE Filed Feb. 27, 1937lNVE NTQR 1-9. E ere21lL]3;C/ch z Y .A MW,

25 ATTORNEY Pmnud Mar. 5, 1940 umrso STATES PATENT OFFICE ILIOTBIORESISTANCE Everett 1!. Bickley, Bale-071N111, Pa. application February27, 1937, Serial No. 128,098 Claims. (01. 201-63) The object of theinvention is to provide im,- provements in electrical resistance unitsor resistors, and more particularly in resistors characterized byrelatively small size but high ohmic 5 rating, such as are employed inassociation with selenium and similar photoelectric or light-responsiveunits, as well as in radio apparatus of various sorts, and innumerableother types of electrical apparatus in which the resistance must bedepended upon to remain constant under all ordinary working conditions,and must, therefore, be maintained at all times in a perfectly drycondition.

In carrying out the invention thus broadly stated, another object is toprovide an improved and simplified method of making the new resistanceunits, the details of which are hereinafter fully set forth. In thisconnection and more specifically, an improved method has been developedwherein the resistance element, of whatever character, can be completelysealed within a glass shell, and wholly without danger of said elementsbeing affected by the temperature at which the glassmelts when saidshell 5 is being sealed.

A further object is to provide a resistor, from which the terminal leadsof relatively small diameter extend for a distance substantially only asfar as the diameter of such leads, in order to eliminate joints and atthe same time provide substantially rigid terminal members, adapted tobe directly engaged by extraneous currentcarrying contact devices.

Still another object is to provide the combination of a substantiallyrigid resistance element, in which only a surface coating serves as theconductor, in combination with a flexible terminal lead, in turncomprising a spiral of greater internal diameter than the externaldiameter of said element, and the opposite sides of said spiralelectrically engaging said coating, when said lead is flexed from aninitial angular position, into a position substantially co-axial withsaid element, and is held in such position by and upon being sealed insaid shell.

With the objects thus broadly stated, the invention comprises furtherdetails of construction and operation, which are hereinafter fullybrought out in the following description, when read in conjunction withthe accompanying drawing, in which Fig. 1 is an elevational view of asection of tubing, partially in section and preferably made of glass;Fig. 2 is a similar view of the same after a lead wire has been sealedin the lower end thereof; Fig. 3 is an elevational view of a slendertubular glass support, a portion of the outer surface of which is shownas being covered with'electrically conductive resistance material, thistube when completely so covered comprising the filament or resistance 5element; Fig. 4 is an elevational view of the second lead wire for thefinished unit; Fig. 5 is a sectional view of the tube and first leadwire, as shown in Fig. 2, positioned within a heating device illustratedby dot-and-dash lines, and 10 showing the solder or equivalentconducting material therein; Fig. 6 is a view similar to Fig. 5, butshowing the method by which the resistance element and second lead wireare inserted into said tube; Fig. 7 is a longitudinal sectional view 16of the improved resistance unit, after the opposite end has been closedby sealing about the second lead wire; Fig. 8 is a side elevational viewof a modified form of lead, operatively supporting the adjacent portionof a resistance eleo ment; Fig. 9 shows a modified method of attaching alead wire to the filament element; Fig. 10 shows a still furthermodification of the same; and Fig. '11 is a longitudinal section throughthe improved resistance unit in which 5 is embodied the last-mentionedmodified lead wire connection. I

Referring to Figs. 1 to! inclusive, the improved method consists intaking the proper length of glass or equivalent tubing l and fusing 30one end 2 so as to close the same, and to simultaneously seal therein alead wire 3 of any desired length initially, but essentially of suchmetal or metallic aloy as possesses substantially the same coeflicientof expansion as that of the tube. 5

The so-called filament or resistance unit, shown in Fig. 3, may likewisecomprise a relatively slender glass tube 4, the outer surface 5 of whichis coated throughout its length with electrically conductive resistancematerial 6, which may com- 40 prise, for purposes of illustration, anextremely finely divided deposit of carbon, such for in stance asfthatcontained in well-known types of black drawing inks, said deposit orcoating obviously being placed upon said last-mentioned tube 45 in auniform layer, in order to provide uniform resistance to an electriccurrent passing therethrough, after which it is of course thoroughlydried.

The second lead wire preferably comprises an an elongated terminalsection 1, having an offset to provide a shoulder 8, through which itmerges into an intermediate, substantially rectilinear portion 9 andthence into a spiral ill, the axis ll of which initially extendsangularly with re- 56 spect to the axis of the terminal section I. In ofsaid leads are substantially equal to their reassembling the improvedresistance unit, the lower or sealed end portion of the tube l ininserted upright in a suitable heating device II, which if desired, maycomprise a small heater energized by electricity, gas, or otherwise.Into this tube is placed either a lump or a small portion or granulatedsolder II or the like, which upon being heated melts and thereby entersinto positive and fixed electrical contact with the inwardly extendingfree end portion of the first lead 3.

With the solder still molten, or in flux, and the tube still positionedin the heating device 12, the spiral portion I is slid lightly over theupper end of the coated resistance element of Fig. 3, while the terminalsection I is manually brought into adjacent parallelism (as shown inFig. 6) with the shank ll of a suitable slender tool, by which theresistance element and second lead are inserted into the tube I.

This tool, in addition to said shank, comprises a handle i and a radialshoulder It, by which the lower end of the resistance element is forcedwell into the molten solder [3, beyond said shoulder said toolterminating in a short slender section H, which enters the bore of theresistance element tube 4. The method of inserting the resistanceelement, tool and second lead into the tube I is clearly shown in Fig.6, wherein it will be noted that the shoulder B of said second leadengages the inner surface of the bore of the surrounding tube, while thediametrically opposite portion of the adjacent convolution of the spiral[0 usually, though not necessarily, engages the opposite portion of theinternal surface of said last-mentioned tube.

With the second lead wire flexed under tension in the position shown inFigs. 6 and '7, it will be obvious that the spiral H1, in being flexedangularly, forms a positive contact throughout two or more substantiallydiametrically opposite areas with the electrically conductive depositupon the filament tube 4. This being accomplished, the tool may bewithdrawn and the upper end l8 of the outer tube sealed about saidsecond lead wire, substantially as shown in Fig. '7, with the resultthat the outer tube and the filament are to all intents and purposesco-axial.

After the improved unit has been assembled, as thus described, thefreely extending portions of the two lead wires 3 and I may be cut off,until they extend beyond the adjacent ends of the outer tube a distancesubstantially equal to the diameter of such respective leads, in orderto form abbreviated terminals, as illustrated in Fig. 11, which are thenadapted to engage extraneous contact members l9, carried by any suitablesupport, indicated by the dot-and-dash line 20. It is not essential thatthe freely extending portions of said leads shall be exactly equal totheir respective diameters, because of the fact that different metalsused for lead wires possess different degrees of hardness or rigidity,The essential qualification or characteristic is that such leads mustextend sufficiently far to serve as positive contacts for the membersl9, thus preventing any portion of the pressure of said members againstsaid leads being shared by the adjacent ends oi. the tube, while at thesame time said leads shall not extend a suflicient distance to permitthem to readily flex laterally upon application of the pressure of themembers l8 against them, wherefore is used the expression that the outerfree portions spective diameters.

Referring to Fig. 8, there is shown a lead wire 2| to the normal innerend of which is secured an initially planular member 22, provided withradially extending fingers 23, which are then curved to form acup-shaped clamp, for yieldingly receiving and frictionally supportingone end of a filament resistance element 24, similar to the element 5,hereinbefore described. This form of terminal is designed to take theplace of the lead wire and solder construction, also hereinbeforedescribed, and it should be noted at this point that while the exteriorsurface of the resistance element is shown only in Fig. 3 as beingcoated with the electrically conductive carbon deposit 8, the filamentresistance elements shown in Figs. 6, 7, 8, 9, l0 and 11 are likewisecoated, but are not so illustrated, because of the impossibility ofshading a solid black surface.

Referring to Fig. 9, there is here shown a slightly modified method ofattaching the first terminal lead wire to the resistance element bymeans of a pre-molded soldered joint, wherein the lead wire 25 extendsupwardly through the lower portion of a suitable heating unit 26, theupper portion of said wire entering a cavity 21 which is open at the topand is adapted to receive and melt solder or the like 28 around saidlead wire, and also in order that the adjacent end of the tubularelement 28 may be inserted into or embedded in said solder, while thesame is still molten or in flux, and furthermore, if desired, broughtinto direct engagement with the adjacent end of the lead wire 25, inorder that said wire and element will maintain a co-axial relationshipafter the solder has cooled and hardened.

Referring to Figs. 10 and 11, the tube I, here shown, is illustrated asbeing closed and sealed at one end 2' about the terminal lead 3' bymeans of solder, or the like i3, and the adjacent end of the tubularresistance element 4 being secured in said solder, as hereinbeforedescribed with respect to Figs. 1 to '1 inclusive. However, in thismodification of the preferred method of assembly, the unit thus formedis then supported in inverted position, so that the opposite or thenlower end of the filament hangs suspended centrally in the tube I, asindicated in Fig. 10. A terminal connection comprising a lead wire 30,carrying a cupshaped holder 3|, for solder or the like 32, is insertedupwardly while this solder is still molten into the then lower open endof the tube I, until the adjacent, end of the tubular filament entersand'becomes embedded within and secured by said solder as it cools. Thisbeing accomplished, the remaining open end of the outer tube may befused and sealed about the lead wire 30, as shown in Fig. *1 1. a

It will be noted particularly in Figs. 7 and 11 that a substantialdistance is provided between the last-sealed tube end 33 and theadjacent end portion of the enclosed resistance element. This is for thepurpose of substantially isolating the latter from the intense heat ofthe former during the process of sealing. More specifically, thetemperature of the glass tube during and at the point of and while beingfused and sealed about the terminal wires 1 and 30 respectively,approxbinder to carry and securely attach the fine particles oi carbonto the filament surface, and which binder would be destroyed by thetemperature of molten glass, with the result that the coating would bedisintegrated, break contact with the adjacent lead wire and makeinefiective the resulting resistance unit.

It is also to be noted that by using relatively short free end portionsof the respective lead wires, preferably cut oil. so as to leaverelatively sharply pointed ends, said lead wires readily cut through anycorrosion upon the mounting contacts IQ of whatever shape they mayassume and thereby insure perfect electrical contact under any and alloperating conditions. This construction obviously eliminates thenecessity of a metal end, such as an external cup or mounted terminal,etc., attached to and enlarging the effective ends of the unit, therebyeliminating anything which can possibly loosen and give resultingtrouble. In short, such terminal leads in direct engagement withsupporting contact members, provides a complete elimination of hiddenand, therefore, inaccessible joints at this point.

Having thus described my invention, what I claim as new and desire toprotect by Letters Patent of the United States is:

1. An electrical resistor comprising in combination, a resistanceelement having lead wires connected thereto extending in oppositedirections, a glass envelope hermetically enclosing said resistanceelement, said wires extending thru said envelope at substantiallyopposite points and terminating outside of said envelope and at adistance of substantially the diameter of said wires from the outsidesurface of said envelope, said wires being sufiiciently rigid to supportthe resistor from opposed electrical contactors pressing against theirends.

2. A resistance unit, comprising a substantially rigid electricalresistance filament, a surrounding hermetically sealed casing, a leadwire sealed through said casing and fixedly connected to one end of saidfilament, and a transversely resilient second lead wire also sealedthrough said casing and provided with a looped portion, adapted whenfiexed with respect to its supporting lead wire to receive and slidablycontact the opposite sides of said filament, to permit relativeexpansion and contraction of said casing with V,

respect to said filament.

3. A resistance unit, comprising a substantially rigid electricalresistance filament, a surrounding hermetically sealed casing, a leadwire sealed through a wall of said casing and fixedly connected to saidfilament, and a second lead wire also sealed through a wall of saidcasing, and provided with a looped inner end adapted to surround theadjacent portion of said filament, and with an intervening ofisetportion adapted to engage the inner surface of said casing, to minimizethe conveyance of vibrations from said casing to said filament.

4. A resistance unit, comprising a substantially rigid electricalresistance filament, a surrounding hermetically sealed casing, a leadwire sealed through a wall of said casing and fixedly connected to saidfilament, and a second lead wire also sealed through a wall of saidcasing, and provided with a looped inner end adapted to surround theadjacent portion of said filament, and with an intervening offsetportion, said offset portion of said last-mentioned lead wire engagingone side and said looped end portion engaging the opposite side of saidcasing, to maintain said casing and filament in substantially axialalignment.

5. A resistance unit, comprising a substantially rigid electricalresistance filament, a surrounding hermetically sealed casing, a leadwire sealed through said casing and fixedly connected to said filament,and a transversely resilient second lead wire also sealed through saidcasing and provided with a spiral end portion of slightly largerdiameter than that of said filament, which when flexed axially receivesand slidably contacts the opposite sides of said filament, to permitrelative expansion and contraction of said casing with respect to saidfilament.

EVERETT H. BICKLEY.

